The present invention relates generally to an apparatus for the detection of toner levels in an electrophotographic printing machine.
Generally, the process of electrophotographic printing and/or copying includes charging a photoconductive surface to a substantially uniform potential or voltage. The charged photoconductive surface is then exposed to record an electrostatic latent image corresponding to an original document to be copied. Thereafter, a developer material is brought into contact with the latent image. The developer material attracts toner particles onto the latent image. The resultant image is then transferred from the charged photoconductive surface onto a copy sheet, to which it is subsequently bonded.
Contaminants, such as paper fragments, developer material, toner and other residue, remain on the photoconductive surface after the image has been transferred to the copy sheet. This residue must be removed from the photoconductive surface prior to the next charging thereof. Typically, a cleaning station is provided within the electrophotographic printing and/or copying machine to remove the residue from the photoconductive surface. The cleaning station generally includes cleaning brushes and a vacuum system. The cleaning brushes dislodge the residue from the photoconductive surface into an air stream created by the vacuum system. The residue is deposited by the air stream into a waste container. The waste container must be emptied when full or nearly full, in order to prevent residual toner particles from being catastrophically distributed throughout the machine. Thus, the level of residual toner within the waste container must be monitored in some way in order to detect when the container is full or nearly full.
One method by which the level of residual toner is conventionally monitored is through the use of an optical monitoring device. Optical devices, however, require frequent cleaning to remove stray contaminants, such as dust and other particles, from the device to ensure proper operation. Further, such optical devices can yield premature or inaccurate indications of a full waste container due to toner dust clinging to the sides of an otherwise empty or only partially full waste container. Such false indications of a full waste container can result in increased machine downtime due to the required operator intervention to clear such a false indication.
Another method by which the level of residual toner is conventionally monitored is through the use of a weighing device which measures the weight of the waste container to thereby indicate when the container is full or nearly full. Such weighing devices require frequent calibration. Furthermore, different types of toner will have different densities. When, for example, a lower density toner is in use, a weight-based monitoring system can result in the waste container being filled with residual toner before the system indicates a full waste container. Such a failure to detect a full waste container results in toner particles being catastrophically distributed throughout the machine, increased machine downtime, and is likely to require a lengthy servicing of the machine.
Yet another method by which the level of residual toner is conventionally monitored is through the use of a capacitive sensor disposed on the outside of and adjacent to the waste container. Such external capacitive sensors are susceptible to electrostatic discharge and other forms of electrical interference which can contribute to an erroneous indication of container status. Further, and similar to optical systems, particles such as stray toner and other particles may become lodged between one or more of the electrodes or plates, and interfere with the operation of the sensor. Moreover, such external capacitive sensors may be bumped and damaged during changing and/or emptying of the waste toner bottle.
Therefore, what is needed in the art is a toner level sensing device that is less affected by stray toner particles and other contaminants.
Furthermore, what is needed in the art is a toner level sensing device that is less sensitive to variations in toner density.
Still further, what is needed in the art is a toner level sensing device that is less susceptible to electrical noise and has a high signal-to-noise ratio.
Moreover, what is needed in the art is a toner level sensing device that is less susceptible to erroneous operation due to electrostatic discharge and other forms of electrical interference.
The present invention provides an apparatus for detecting the level of material within a container.
The invention comprises, in one form thereof, an electrically conductive container body that defines a container cavity and an orifice. A sensor assembly includes a holder and a probe. The holder is sealingly associated with the orifice. The probe is disposed within the holder. The holder electrically isolates the probe from the container body. The probe senses a level of material within the container cavity.
An advantage of the present invention is that the operation of the toner level detecting assembly is less affected by stray toner particles and other contaminants.
Another advantage of the present invention is that the toner level detecting assembly is less sensitive to variations in toner density.
Yet another advantage of the present invention is that the toner level detecting assembly is less susceptible to electrical noise and has a high signal-to-noise ratio.
A still further advantage of the present invention is that the toner level detecting assembly is less susceptible to erroneous operation due to electrostatic discharge and other forms of electrical interference.